Modern electronics devices, such as integrated circuits ("ICs") or semiconductor "chips" are rapidly increasing in production quantity and functionality, while decreasing in size and unit cost. For increasing productivity of the electronic devices, it is required to decrease test cost and test time. This can best be accomplished with fully automated electronic device test systems.
In a conventional test system, electronic devices to be tested are removed from their container, usually called a "magazine," and separated from one another by the force of gravity. That is, the electronic device to be tested is positioned initially at a vertically higher position than the test head and, by its own weight, is separated from the other devices such that it slidably descends to the test head. After the test, the electronic device descends further, due to gravity, to a lower position than the test head so as to be sorted depending on the test results.
Such conventional device test systems, which utilize the force of gravity to separate and transfer the electronic devices, has two inherent disadvantages. First, since modern electronic devices have become smaller and lighter than before, an individual electronic device does not have sufficient weight to efficiently separate from the others. This causes "jamming," wherein two or more electronic devices stick together and cannot separate from one another. If such jamming occurs, it is usually necessary to stop the operation of the test system to clear the jam, thus causing a serious loss of time and efficiency. Furthermore, the risk of jamming is greatly increased due to the configuration of the new types of electronic devices to be tested. For example, one new type of electronic device has electric leads (pins), not just on two sides of the chip package (as in the conventional dual-in-line or "DIP" package), but on all sides of the package. Thus, a plastic-chip-carrier ("PLCC") package has electric leads on all four sides of the package, thus inherently causing the pins to contact one another and increasing the likelihood of jamming.
Second, to avoid the jamming, the outer surface of the electronic device must be made sufficiently smooth so as not to cause any friction or entanglement with other devices. However, this is also impractical since the plastic molded packages of the devices inevitably have some burrs remaining from the production process. It is not economically practical to completely eliminate such burrs. Therefore, the electronic device test systems which rely on the force of gravity for device separation and transfer suffer from a few serious disadvantages in view of modern techniques in electronic device packaging.
A further inefficiency in the testing of electronic devices involves the carrier in which the devices are placed prior to testing. Today, many different types of electronic devices are being utilized; whereas, in previous years, only the standard DIP package was commonly utilized. Electronic devices to be tested are usually put into market in a container called a device magazine or an IC magazine. Therefore, in testing electronic devices with typical test systems, it is necessary to take the electronic devices to be tested out of the device magazine prior to testing, and then replace them for shipping. In the conventional device magazine, the outer shape and size varies depending on the kind and shape of the electronic devices to be contained therein. If the device magazine must be changed each time a differently configured chip is tested, a serious increase in production time and expense will result.
Thus, there is a need for a more versatile electronic test system which can efficiently transfer electronic devices without relying on the force of gravity and, at the same time, accommodate a variety of chip configurations.